# Occurrence modes of gold and relevant analytical methodologies

## TL;DR

This paper reviews methods for analyzing gold's chemical phases in ores to improve processing decisions and environmental safety.

## Contribution

The paper highlights challenges in current gold phase analysis and suggests future directions for greener and more accurate methods.

## Key findings

- Current gold phase analysis methods use sequential selective extraction with solvents like iodine and cyanide.
- Existing methods face issues like environmental risks and low accuracy due to complex gold occurrences.
- Future research should focus on green reagents and better integration of characterization and pretreatment.

## Abstract

Gold chemical phase analysis is a key technique for determining the occurrence modes of gold in ores and guiding mineral processing decisions. Research in this field is generally divided into physical and chemical analysis. Chemical phase analysis operates on the principle of sequential selective extraction, using specific solvent sequences (e.g., iodine solution, cyanide, sodium thiosulfate) to selectively dissolve different host minerals, thereby enabling the quantitative determination of phases such as free gold, sulfide-occluded gold, and silicate-occluded gold. For measuring gold in different phases, methods including amalgamation-iodine leaching, amalgamation-thiourea-iodine leaching, amalgamation-bromine-iodine leaching, and cyanidation have been established. However, current methods face several challenges: reliance on toxic reagents like mercury and cyanide poses environmental and safety risks; analytical procedures are complex, and accuracy is often compromised by the complexity of gold occurrence, insufficient solvent selectivity, and the preg-robbing effect; furthermore, pretreatment is costly and prone to causing pollution. Future research should focus on developing green, low-toxicity leaching reagents and fostering closer integration between precise phase characterization and efficient pretreatment technologies. This will enhance analytical accuracy, efficiency, and environmental friendliness, thereby supporting the green and efficient utilisation of refractory gold resources.

Gold chemical phase analysis quantifies different gold occurrence states through selective dissolution to assess ore processability.